104 lines
3.6 KiB
C++
104 lines
3.6 KiB
C++
// Solutions to the Advent Of Code 2024.
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// Copyright (C) 2025 Stefan Müller
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//
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// This program is free software: you can redistribute it and/or modify it under
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// the terms of the GNU General Public License as published by the Free Software
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// Foundation, either version 3 of the License, or (at your option) any later
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// version.
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//
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// This program is distributed in the hope that it will be useful, but WITHOUT
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// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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// FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License along with
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// this program. If not, see <http://www.gnu.org/licenses/>.
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#include <aoc/DiskFragmenter.hpp>
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const std::string DiskFragmenter::getPuzzleName() const
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{
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return "Day 9: Disk Fragmenter";
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}
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const std::string DiskFragmenter::getInputFileName() const
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{
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return "disk_fragmenter.txt";
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}
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void DiskFragmenter::processDataLine(const std::string& line)
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{
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//size_t maxIdNumber{ line.size() / 2 };
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// Index of the first unprocessed digit in the disk map.
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size_t front{ 0 };
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// ID number of the file 'front' refers to (when 'isFile == true'). Equivalent to 'front / 2', but calculated
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// incrementally.
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size_t frontIdNumber{ 0 };
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// Index of the last unprocessed digit in the disk map.
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size_t back{ line.size() - 1 };
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// Number of remaining fragmented blocks in the file that 'back' refers to (when 'isFile == true').
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int nRemainingBackBlocks{ getDigit(line, back) };
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// ID number of the file 'back' refers to (when 'isFile == true'). Equivalent to 'back / 2', but calculated
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// incrementally.
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size_t backIdNumber{ line.size() / 2 };
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// Current block position.
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size_t position{ 0 };
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bool isFile{ true };
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while (front < back)
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{
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if (isFile)
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{
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// Adds the checksum for the file at 'front'.
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int nFileBlocks = getDigit(line, front);
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part1 += calcChecksumPart(frontIdNumber, nFileBlocks, position);
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frontIdNumber++;
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}
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else
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{
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int nFreeBlocks = getDigit(line, front);
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while (nFreeBlocks > 0)
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{
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if (nFreeBlocks >= nRemainingBackBlocks)
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{
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// Adds the checksum for all the blocks of the file at 'back'.
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part1 += calcChecksumPart(backIdNumber, nRemainingBackBlocks, position);
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backIdNumber--;
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nFreeBlocks -= nRemainingBackBlocks;
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back -= 2;
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nRemainingBackBlocks = getDigit(line, back);
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}
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else
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{
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// Adds the checksum for the blocks of the file at 'back' that fit into the empty blocks at 'front'.
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part1 += calcChecksumPart(backIdNumber, nFreeBlocks, position);
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nRemainingBackBlocks -= nFreeBlocks;
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nFreeBlocks = 0;
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}
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}
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}
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front++;
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isFile = !isFile;
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}
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// Adds the checksum for the remaining blocks of the file at 'back'.
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part1 += calcChecksumPart(backIdNumber, nRemainingBackBlocks, position);
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}
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void DiskFragmenter::finish()
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{
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}
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int DiskFragmenter::getDigit(const std::string& line, const size_t index) const
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{
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return line[index] - '0';
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}
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long long int DiskFragmenter::calcChecksumPart(const size_t idNumber, const int nBlocks, size_t& position) const
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{
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position += nBlocks;
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return idNumber * ((nBlocks * (2 * position - nBlocks - 1)) / 2);
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}
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